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Homework Help: Polar Coordinates Arc Length

  1. Nov 10, 2008 #1
    1. The problem statement, all variables and given/known data

    Find The length of r=sin³(x/3) 0<x<3pi/2

    2. The attempt at a solution

    well first i found r'=3.cos(x/3).1/3.sin²(x/3)=cos(x/3)sin²(x/3)

    then i put the formula

    integral of radical (r'²+r²)dx and i'm stuck here

    any help?
  2. jcsd
  3. Nov 10, 2008 #2


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    Science Advisor
    Homework Helper

    Hi JosephR! :smile:

    Hint: sin6(x/3) = sin²(x/3)sin^4(x/3) :wink:
  4. Nov 10, 2008 #3
    hey tiny-tim:)

    i knew this but it would take some time to be solved !!

    because sin²(x/3)=[1-cos(2x/3)]/2

    anyway thanks buddy !!
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